diff --git a/src/vault/euph.rs b/src/vault/euph.rs
index bc08c13..642f3c3 100644
--- a/src/vault/euph.rs
+++ b/src/vault/euph.rs
@@ -624,14 +624,6 @@ impl EuphRequest {
             [&room],
         )?;
 
-        tx.execute(
-            "
-            DELETE FROM euph_trees
-            WHERE room = ?
-            ",
-            [&room],
-        )?;
-
         tx.commit()?;
         Ok(())
     }
@@ -683,26 +675,6 @@ impl EuphRequest {
                 real_client_address = :real_client_address
             "
         )?;
-        let mut delete_trees = tx.prepare(
-            "
-            DELETE FROM euph_trees
-            WHERE room = ? AND id = ?
-            ",
-        )?;
-        let mut insert_trees = tx.prepare(
-            "
-            INSERT OR IGNORE INTO euph_trees (room, id)
-            SELECT *
-            FROM (VALUES (:room, :id))
-            WHERE NOT EXISTS(
-                SELECT *
-                FROM euph_msgs
-                WHERE room = :room
-                AND id = :id
-                AND parent IS NOT NULL
-            )
-            ",
-        )?;
 
         let own_user_id = own_user_id.as_ref().map(|u| &u.0);
         for msg in msgs {
@@ -728,13 +700,6 @@ impl EuphRequest {
                 ":real_client_address": msg.sender.real_client_address,
                 ":own_user_id": own_user_id, // May be NULL
             })?;
-
-            if let Some(parent) = msg.parent {
-                delete_trees.execute(params![room, msg.id])?;
-                insert_trees.execute(named_params! {":room": room, ":id": parent})?;
-            } else {
-                insert_trees.execute(named_params! {":room": room, ":id": msg.id})?;
-            }
         }
 
         Ok(())
diff --git a/src/vault/prepare.rs b/src/vault/prepare.rs
index 0875db7..75f351f 100644
--- a/src/vault/prepare.rs
+++ b/src/vault/prepare.rs
@@ -3,8 +3,7 @@ use rusqlite::Connection;
 pub fn prepare(conn: &mut Connection) -> rusqlite::Result<()> {
     println!("Opening vault");
 
-    // This temporary table has no foreign key constraint on euph_rooms since
-    // cross-schema constraints like that are not supported by SQLite.
+    // Cache ids of tree roots.
     conn.execute_batch(
         "
         CREATE TEMPORARY TABLE euph_trees (
@@ -28,6 +27,41 @@ pub fn prepare(conn: &mut Connection) -> rusqlite::Result<()> {
             WHERE parents.room = euph_msgs.room
             AND parents.id = euph_msgs.parent
         );
+
+        CREATE TEMPORARY TRIGGER et_delete_room
+        AFTER DELETE ON main.euph_rooms
+        BEGIN
+            DELETE FROM euph_trees
+            WHERE room = old.room;
+        END;
+
+        CREATE TEMPORARY TRIGGER et_insert_msg_without_parent
+        AFTER INSERT ON main.euph_msgs
+        WHEN new.parent IS NULL
+        BEGIN
+            INSERT OR IGNORE INTO euph_trees (room, id)
+            VALUES (new.room, new.id);
+        END;
+
+        CREATE TEMPORARY TRIGGER et_insert_msg_with_parent
+        AFTER INSERT ON main.euph_msgs
+        WHEN new.parent IS NOT NULL
+        BEGIN
+            DELETE FROM euph_trees
+            WHERE room = new.room
+            AND id = new.id;
+
+            INSERT OR IGNORE INTO euph_trees (room, id)
+            SELECT *
+            FROM (VALUES (new.room, new.parent))
+            WHERE NOT EXISTS(
+                SELECT *
+                FROM euph_msgs
+                WHERE room = new.room
+                AND id = new.parent
+                AND parent IS NOT NULL
+            );
+        END;
         ",
     )?;